Comparing biofuels through the lens of sustainability: A data envelopment analysis approach

Switchgrass (Panicum virgatum L.) is undergoing development as a biomass crop to support conversion of cellulosic biomass to energy. To avoid the competition of biomass with food or feed crops, most commercialization proposals suggest that switchgrass should be grown exclusively on marginal lands that are not fit for food or feed production. The objective of this study was to investigate the potential for cultivar ́ environment interactions that would affect the methods and approaches for breeding and evaluating switchgrass cultivars, including both upland and lowland types, for high-input versus low-input types of environments. Biomass yield was measured on 14 cultivars that were present in 28 replicated field experiments representing seven regions, ranging from 75 to 100° W and spanning USDA Hardiness Zones 4 through 7. Region was the most important environmental factor interacting with cultivars, supporting the idea that the north-central and northeastern United States should have independent switchgrass breeding programs. Cultivars interacted with soil phosphorus concentration in New Jersey and with depth of the A and B horizons in New York and showed mild interactions with rate of nitrogen fertilizer at several locations. Cultivar rank correlation coefficients between the two rates of nitrogen fertilization (100 vs. 0 kg N ha−1) ranged from 0.23 to 0.88, suggesting a possible benefit to breeding and selection without applied nitrogen fertilizer. M.D. Casler, USDA-ARS, 1925 Linden Dr., Madison, WI 537061108; S. Sosa, 294 Lamplighter Ln., Marietta, GA 30067; L. Hoffman, Rutgers Univ., Dep. of Plant Biology and Pathology, 59 Dudley Rd., Foran Hall, New Brunswick, NJ 08901; H. Mayton, Cornell Univ., Plant Pathology and Plant-Microbe Biology Section, 356 Plant Science, Tower Road, Ithaca, NY 14853; C. Ernst, Ernst Conservation Seeds, 8884 Mercer Pike, Meadville, PA 16335; P.R. Adler, USDA-ARS, Pasture Systems and Watershed Management Research Unit, University Park, Pennsylvania 16802; A.R. Boe, South Dakota State Univ., Dep. of Plant Science, Agricultural Hall, Brookings, SD 57007; S.A. Bonos, Rutgers Univ., Dep. of Plant Biology and Pathology, 59 Dudley Rd., Foran Hall, New Brunswick, NJ 08901. Received 23 Aug. 2016. Accepted 29 Dec. 2016. *Corresponding author (mdcasler@wisc.edu, michael.casler@ars. usda.gov). Assigned to Associate Editor Hem Bhandari. Abbreviations: GE, genotype ́ environment; HYE, high-yield environment; LYE, low-yield environment; PLS, pure live seed. Published in Crop Sci. 57:821–832 (2017). doi: 10.2135/cropsci2016.08.0698 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. Published February 23, 2017

/pdf/biomass-yield-of-switchgrass-cultivars-under-high-versus-low-3pwuhcsorg.pdf

Biomass Yield of Switchgrass Cultivars under High- versus Low-Input Conditions

The environmental costs and benefits of producing bioenergy crops can be measured both in kterms of the relative effects on soil, water, and wildlife habitat quality of replacing alternate cropping systems with the designated bioenergy system, and in terms of the quality and amount of energy that is produced per unit of energy expended. While many forms of herbaceous and woody energy crops will likely contribute to future biofuels systems, The Dept. of Energy`s Biofuels Feedstock Development Program (BFDP), has chosen to focus its primary herbaceous crops research emphasis on a perennial grass species, switchgrass (Panicum virgatum), as a bioenergy candidate. This choice was based on its high yields, high nutrient use efficiency, and wide geographic distribution, and also on its poistive environmental attributes. The latter include its positive effects on soil quality and stabiity, its cover value for wildlife, and the lower inputs of enerty, water, and agrochemicals required per unit of energy produced. A comparison of the energy budgets for corn, which is the primary current source of bioethanol, and switchgrass reveals that the efficiency of energy production for a perennial grass system can exceed that for an energy intensive annual row crop by as much as 15 times. In additions reductions in CO{sub 2} emission, tied to the energetic efficiency of producing transportation fuels, are very efficient with grasses. Calculated carbon sequestration rates may exceed those of annual crops by as much as 20--30 times, due in part to carbon storage in the soil. These differences have major implications for both the rate and efficiency with which fossil energy sources can be replaced with cleaner burning biofuels.

/pdf/evaluating-environmental-consequences-of-producing-1f0aaqsdaj.pdf

Evaluating environmental consequences of producing herbaceous crops for bioenergy

The perennial C4 Miscanthus spp. is used in China for bio‐fuel production and its ecological functions. However, questions arise as to its economic and environmental sustainability in abandoned farmland where the costs should be very low. Little is known about its yield performance and effects on soil properties when it was harvested annually without any inputs in China. To address these questions, an experiment was implemented for 12 years on annually harvested Miscanthus sacchariflorus planted in 2006 and managed without fertilization, irrigation, or any other inputs. We determined biomass yields each year, biomass allocation, and soil properties before and after its cultivation. Biomass yields of M. sacchariflorus reached a peak value (29.67 t/ha) 3 years after cultivation and was maintained at a stable level (averaged 22.22 t/ha) during 2012–2017. Its root shoot ratio increased due to more biomass allocated below‐ground with time. Long‐term cultivation of M. sacchariflorus increased organic carbon contents, pH (for the absence of fertilization), microbial carbon, nitrogen and phosphorus contents, and soil carbon nitrogen ratios (0–100 cm). Soil bulk density was decreased significantly (p < .05) independent of soil depths. Annual harvest did not reduce total nitrogen and phosphorus, available nitrogen, and potassium, but total the potassium content of soil (0–100 cm). Cultivation of M. sacchariflorus increased available phosphorus contents in 40–100 cm soil and reduced that value in 20–40 cm soil. Biological nitrogen fixation provided ~218.74 kg ha−1 year−1 (1 m depth) nitrogen for the system offsetting nitrogen export by biomass harvest and stabilizing nitrogen levels of soil. In conclusion, M. sacchriflorus exhibited sustainable biomass yields and ameliorated soil properties but the decrease of total potassium contents after 12 years’ cultivation without any input. These conclusions could provide important information timely for the government and encourage farmers to promote large‐scale utilization of M. sacchriflorus on the abandoned farmland in China.

Miscanthus sacchriflorus exhibits sustainable yields and ameliorates soil properties but potassium stocks without any input over a 12‐year period in China

Background: Government-funded schemes introduced to encourage new afforestation (exotic and indigenous) include the establishment of low-density plantings (less than 1100 stems ha–1) of manuka (Leptospermum scoparium Forster et Forster f.) on steeplands with severe erosion susceptibility and considered marginal for pastoral production. There is, however, little quantitative data to establish when (i.e., how many years after planting) these plantings likely afford effective mitigation against the initiation of shallow landslides.Methods: Permanent sample plots [PSPs] were established within manuka plantings established in northern Hawke’s Bay, New Zealand, where above-ground growth metrics were recorded for plantings on three landform units including interfluve ridges, colluvial slopes, and slopes affected by landslides. The root systems of a small sub-set of manuka were hand-excavated and whole plants destructively sampled for analysis of differences in allometric relationships by year, between landforms, and for comparison of the above-ground components of trees within PSPs.Results: Six years after planting, interfluves and colluvial slopes were understocked by between 10 and 25%, and by up to 45% on sites previously affected by landslides. Root collar diameter (RCD) explained between 92 and 99% of the variation in manuka biomass. The overall above- and below-ground metrics for manuka excavated from interfluves were significantly greater (P<0.05) than those excavated from landslides. Irrespective of landform type, the greatest proportion of the mean total root length and biomass was found in the top 0–0.5 m of the soil profile, within a 0.5-m radius of the stump, and importantly, no roots were found below 1 m depth. The timing (years after planting) to attain canopy closure and root occupancy, if stands of m?nuka were to remain fully stocked, varies between landforms and would likely occur between 6.5 and 9 years after planting. However, variable rates in planting density, and of plant mortality, resulting in under-stocking would significantly delay this timing, particularly on landslide-affected slopes.Conclusions: Manuka planted at densities below 1100 stems ha–1 are unlikely to provide effective erosion mitigation on steep land until significant root mass develops below the depth of the shear plane at which most landslides occur. Increasing the planting density, reducing early seedling mortality by better management of weed competition, and/or their replacement (blanking) would probably improve the erosion mitigation effectiveness of future low-density manuka plantings.

http://nzjforestryscience.nz/index.php/nzjfs/article/download/82/33

Potential effectiveness of low-density plantings of manuka (Leptospermum scoparium) as an erosion mitigation strategy in steeplands, northern Hawke’s Bay, New Zealand

On-farm assessments of Miscanthus × giganteus growth and nutrient export across a wide range of management and environmental conditions are needed to determine and model how this crop performs and where it should be placed on the landscape. Therefore, Miscanthus growth and nutrient concentration and nutrient export at harvest were monitored during 2014 and 2015 at several landscape positions within 22 commercial production fields in central and southwestern Missouri and northeast Arkansas. Miscanthus shoot density and/or yield were best when it was grown: (i) following pasture converted to annual row crops or following row crops, (ii) on soils with colluvium parent material, (iii) on north-facing backslopes or footslopes, (iv) on soils with medium to fine texture, and (v) on well-drained/high runoff/low available water soils. Factors influencing nutrient concentrations varied by nutrient, but all concentrations consistently decreased as stands matured and most were more influenced by weather than were yield or nutrient export. Most effects on nutrient export were similar to effects on yield, but some nutrient exports were also influenced by manure history and weather conditions. Overall, cropping history prior to Miscanthus, landscape position, and soil properties such as parent material, soil textural class, and drainage class had the largest influence on Miscanthus growth and nutrient concentrations and exports. Weather conditions and inferior soils did not strongly influence Miscanthus production, but excessive soil moisture caused by various soil and weather factors often limited its growth. Thus, Miscanthus may be especially well-suited following annual crops on erosion-prone soils that drain well and have slope. These results will assist with the strategic cultivation of Miscanthus on Midwest landscapes.

Miscanthus × Giganteus Growth and Nutrient Export on 22 Producer Fields

Switchgrass (Panicum virgatum L.) is an attractive bioenergy crop option for eroded portions of claypan landscapes where grain crop production is marginally profitable. Topsoil thickness above the claypan, or depth to claypan (DTC), can vary widely within fields, and little information exists on its impacts on N management of switchgrass. Therefore, a study was conducted at the University of Missouri South Farm near Columbia, Missouri, to determine whether topsoil thickness influenced fertilizer N requirements of switchgrass. Switchgrass was planted in 2009 on main plots with a range of DTC classified as exposed ( 30 cm) and was harvested annually at postdormancy during 2011 to 2015. Three split-plot treatments were 0, 67, or 101 kg N ha−1 applied annually in May, and a fourth was three intercropped native legumes as the N source. Across years, the legume treatment apparently supplied no N because it produced the same or less switchgrass yield than the nonfertilized treatment. Topsoil proved valuable as switchgrass yield, nutrient removal, and profit usually increased as DTC increased. Fertilization with 101 kg N ha−1 on exposed, shallow, or moderate DTC and 67 kg N ha−1 on deep DTC was required to obtain the highest biomass yield, but it also increased nutrient removal. Strikingly, profit across years was negative for the legume treatment and highest with no fertilizer on all DTC classes. Therefore, improvements are needed before intercropped legumes are profitable, and N fertilization may be needed only periodically to maximize switchgrass profit on claypan soils.

Topsoil Thickness Influences Nitrogen Management of Switchgrass

Topsoil Thickness and Harvest Management Influence Switchgrass Production and Profitability

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Miscanthus × Giganteus Growth and Nutrient Export on 22 Producer Fields

Topsoil Thickness Influences Nitrogen Management of Switchgrass

Topsoil Thickness and Harvest Management Influence Switchgrass Production and Profitability